The Federal Communications Commission (FCC) mandates the technical standards for the display of closed captioning information encoded and transmitted within the television signal. The Advanced Television Systems Committee (ATSC) and the Society of Cable Telecommunications Engineers (SCTE) have defined the technical standards for wrapping closed captioning information within a compressed video signal.
The National Television System Committee (NTSC) developed the closed captioning concepts for analog television signals. The Electronic Industries Alliance (EIA) developed EIA-608 (also known as line 21 captions) as the standard for closed captioning for NTSC television broadcasts in the United States and Canada. The FCC required EIA-608 to be implemented in most television receivers made in the United States.
Digital Television Closed Captioning (DTVCC), formerly known as Advanced Television Closed Captioning (ATVCC), is the migration of NTSC closed captioning to the high-definition digital television environment defined by ATSC. The EIA developed EIA-708 (also known as Consumer Electronics Association CEA-708) as the standard for closed captioning for ATSC digital television streams in the United States and Canada. The FCC requirements specify the use of EIA-708 caption decoders in all 13-inch (33-cm) diagonal or larger digital televisions. Furthermore, the FCC requirements specify that some broadcasters caption a specific percentage of their broadcasts.
The transition from analog to digital television transmissions has made EIA-608 less prevalent as digital televisions replace analog televisions. In addition, legacy cable and satellite set-top boxes implement an older caption transport standard developed by SCTE (SCTE-20) that differs from the broadcast caption transport standard (A/53). Hence, if the broadcast stream is simply retransmitted (or even rate-shaped) over the cable or satellite network, these legacy set-top boxes will not be able to extract and decode broadcast captions. On the other hand, the newer SCTE standard (SCTE-21) is the same as the ATSC standard for captions, and thus newer cable boxes which usually implement SCTE-21 can decode the encapsulated captions. An SCTE-20 wrapper can only carry EIA-608 compliant captions that are defined for analog transmission and display on analog receivers, and an SCTE-21 (A/53) wrapper can carry both EIA-608 and EIA-708 captions, the latter being defined for rendering on newer digital television set-top boxes.
Thus, there is a need for a system and method for caption formatting to ensure that broadcast captions are carried in both legacy and the new formats, such that they are decodable by all cable or satellite receivers. The presently disclosed invention satisfies this demand.